Ahmad Posted January 9, 2003 Posted January 9, 2003 It is logical that a 'species', by definition, must have all its needs (i.e.: natural selection). But why is it that we almost need all we have? Whenever something is discovered in a living thing, it is always paired to a function, or said to be of an unknown function. We never say that it doesn't have a function!
Radical Edward Posted January 9, 2003 Posted January 9, 2003 because something with no function would not be selected for, and besides, these things don't come about overnight.
fafalone Posted January 10, 2003 Posted January 10, 2003 If something doesn't truly doesn't have a need now, it once did; and logic dictates unless it was harmful it wouldn't be selected out.
Ahmad Posted January 15, 2003 Author Posted January 15, 2003 From my understanding of natural selection, it can only select things out, not select things in. So as fafalone said, if it is not harmful (i.e.: causes distinction of the species), it won't be selected out. Now, fafalone, you said that if something doesn't have a need now, it once did. Did you mean once in the history of a specific species, or once as in the species we originated from?
Giles Posted January 15, 2003 Posted January 15, 2003 If a gene is no longer under selective pressure it will tend to mutate into uselessness over time. This includes the part of the genome that controls its expression. This is what a lot of junk DNA is. You can't discriminate species over time meaningfully; there is no distinct cut-off between a population being of one species and it being of another due to evolution.
mister_me Posted January 15, 2003 Posted January 15, 2003 Originally posted by Ahmad It is logical that a 'species', by definition, must have all its needs (i.e.: natural selection). But why is it that we almost need all we have? Isn't it amazing? Maybe an intelligent being created this planet the way it is so that we would have everything that we need. I don't think that they would just create us and leave us on a wasteland of a planet, would they now? That's not very resposible of an over-intelligent being.
Ahmad Posted January 16, 2003 Author Posted January 16, 2003 Hi Giles, I get your point. I see it amazing though. There are always those who are asking, why don't we witness a mutation to something good? Why can't we find a realy example of a mutation that happened and created a big leap from a species to another? One that changes even the number of chromosomes and the distribution of the genes over the chromosomes? And the answer is that these things take time. Why is it then that it doesn't take mutations that much time to remove extra features that we don't need. It happens in no time that we can't even find something without such an extra feature.
Giles Posted January 16, 2003 Posted January 16, 2003 It's hard to speculate about what organisms 'need'. After all, you only need less than half of your lung capacity to survive. Another problem is that characteristics have to arise through adaptation. That means they have to fit the enviroment. There are few characteristics so specialised that they would be completely useless in an enviroment that the organism could survive in. Nor are many organisms likely to experience such a drastic, unexpected change in habitat in one life time.
Ahmad Posted January 16, 2003 Author Posted January 16, 2003 OK. You can add to that this questions: How did we aquire these features that makes our lives more convenient, yet we could still survive without them, although life would have been harder. For example, when you want to exercise, just by thinking about starting, your muscles will get more blood flow. The same thing for the lungs' size. We don't need it to survive, but we need it to live a better life. How come we still have these features even though we don't need them to survive? Why don't we have other features like these that are not useful to us in any way, and that wouldn't make our lifes better? Looking at a much lower level, we have 20 amino acids that we need to code for in our DNA. We use three nucleotides for each amino acid. Why did it happen that we have exactly three nucleotides? 1 for an amino acid wouldn't be sufficient, 2 for an amino acid wouldn't be sufficient either, 3 would be sufficient, but why not 4 or 5? This all makes me think life is very concise. Gene knock-out animals always have several problems. I even heared that cancer risks are higher in people that had their appendix removed! For all these things, I can't find an answer in natural selection. They all make me think that life is concise, and thus can never come randomly.
Radical Edward Posted January 16, 2003 Posted January 16, 2003 Originally posted by Ahmad Looking at a much lower level, we have 20 amino acids that we need to code for in our DNA. We use three nucleotides for each amino acid. Why did it happen that we have exactly three nucleotides? 1 for an amino acid wouldn't be sufficient, 2 for an amino acid wouldn't be sufficient either, 3 would be sufficient, but why not 4 or 5? 3 is the simplest possible system, and it requires the simplest proteins to read the DNA. everything else is just redundancy and waste energy, and so an organism just using 3 would be the most efficient, and most likely to reproduce. one would expect. Plus it depends on how the organisms evolved in the first place. I'm not sure off hand what the definition of an amino acid is, but say life used more, then it would need more nucleotides....
Giles Posted January 17, 2003 Posted January 17, 2003 Generally, higher capacity, redundancy and safety margins are better - you can't win a marathon on one lung. You think about exercise when you need to exercise, and it prepares you (think how useful this would be in predator-prey interactions.) Your immune system can handle more diseases than it will ever encounter. You can survive injuries. I suspect the amino acid code is a matter of chance in some degree. once you've got one you can see how hard it would be to change. Nevertheless it does vary to some extent. There are also certain likely pressures on it. It should be mentioned it's not exactly the same in all organisms, but it's always three base pairs to a codon. There are more than four bases though, if not more than four at a time, and more than 20 amino acids. it's probably at least partly a matter of stability. A redundant coding system is more stable in the face of mutation (please note that natural selection favours a LOW rate of mutation in the short term - higher organisms have other ways of generating variation). Conversely, four base types is more concise than two (2 bits/pair rather than 1). Because of the way pair matching is carried out, another base with similar chemical properties to an existing one would be a liability. Your post seems a little confused. Life is no as concise as it could plausibly be with a similar underlying chemical structure; nor is it very long-winded (unlike me). Finally, it shows signs of being constrained by past design. I'm not sure there's much problem for evolutionary theory in that. I think we both need to learn more biochemistry to discuss this with confidence.
Ahmad Posted January 18, 2003 Author Posted January 18, 2003 Originally posted by Giles Generally, higher capacity, redundancy and safety margins are better - you can't win a marathon on one lung. You think about exercise when you need to exercise, and it prepares you (think how useful this would be in predator-prey interactions.) Your immune system can handle more diseases than it will ever encounter. You can survive injuries. So they do serve a purpose? Even redundancy serves a purpose. Either to make our lifes easier, or that we needed it to survive. There is a muscle in the midline, just above the pubic bone called pyramidalis. Only 40% of the population have it. It tenses the long line of connective tissue in the midline, called lina alba. So it makes movement easier, but it is not neccessary for survival. There are other things too that could have been selected out, but are still there, and they do serve a purpose. I suspect the amino acid code is a matter of chance in some degree. once you've got one you can see how hard it would be to change. Nevertheless it does vary to some extent. There are also certain likely pressures on it. What I mean is, why did the system develop this way in the first place. Why didn't it develop in 4 bases for a codon instead? It should be mentioned it's not exactly the same in all organisms, but it's always three base pairs to a codon. There are more than four bases though, if not more than four at a time, and more than 20 amino acids. Yeah, always three bases per a codon, but some codons code for different amino acids in different organisms. In the DNA, there is only the four bases, unless there is a mutation (somtimes a cytosine is converted into a thymine). In RNA, however, there are more bases. it's probably at least partly a matter of stability. A redundant coding system is more stable in the face of mutation (please note that natural selection favours a LOW rate of mutation in the short term - higher organisms have other ways of generating variation). What I'm saying is that the coding system is not actually redundant. There are only 64 codons, it couldn't have been less, because it would be 16, which is not enough. But it is not any more than that. Conversely, four base types is more concise than two (2 bits/pair rather than 1). Because of the way pair matching is carried out, another base with similar chemical properties to an existing one would be a liability. So, it is concise in here too. Your post seems a little confused. Life is no as concise as it could plausibly be with a similar underlying chemical structure; nor is it very long-winded (unlike me). Finally, it shows signs of being constrained by past design. I'm not sure there's much problem for evolutionary theory in that. Well, that's the point. It is more relative in here. We can't say if this is the most concise system or not, because for that we need to understand the purpose of every piece of the system. Still, when we are talking probabilities, the overall picture should be that everything should add up to seem almost exactly between complete conciseness and the opposite of that. And it seems to me that it is much nearer to complete conciseness. And that is for the facts I'm mentioning. The only explanation I can find for that based on evolution is that evolution has been lucky most of the time. I think we both need to learn more biochemistry to discuss this with confidence. I'm not sure if I'm gonna ever learn any more of that. We have already finished the molecular biochemistry unit. Unless I make it my specialty after I graduate (which is not very unlikely), I might never come to that later.
Radical Edward Posted January 18, 2003 Posted January 18, 2003 Originally posted by Ahmad What I mean is, why did the system develop this way in the first place. Why didn't it develop in 4 bases for a codon instead? What I'm saying is that the coding system is not actually redundant. There are only 64 codons, it couldn't have been less, because it would be 16, which is not enough. But it is not any more than that. there is no 'why' in this case. It's the way things are.
Giles Posted January 19, 2003 Posted January 19, 2003 Originally posted by Ahmad So it makes movement easier, but it is not neccessary for survival. There are other things too that could have been selected out, but are still there, and they do serve a purpose. Species vary, as novel adaptations take time to spread, and often don't come to characterise the population. There are two obvious reasons for this, and the third less obvious reason that an unvarying population is not always stable (i.e. the more frequent a strategy is, the less advantage it occurs.) Originally posted by Ahmad What I'm saying is that the coding system is not actually redundant. There are only 64 codons, it couldn't have been less, because it would be 16, which is not enough. But it is not any more than that. It is redundant. It only couldn't have been fewer if we were stuck with 4 bases in two pairings, and between 17 and 64 amino acids. That isn't neccesarily something that had to happen. In fact the whole genetic system might have been wildly different. Originally posted by Ahmad The only explanation I can find for that based on evolution is that evolution has been lucky most of the time. Anthropic principle.
Ahmad Posted January 20, 2003 Author Posted January 20, 2003 OK then .. Why is it that we have voluntary control over defecation and urination? What kind of pressures is keeping that?
Radical Edward Posted January 20, 2003 Posted January 20, 2003 Originally posted by Ahmad OK then .. Why is it that we have voluntary control over defecation and urination? What kind of pressures is keeping that? would you go out with a girl who kept crapping herself and peeing her pants? no? neither would I. and the uses for it in nature are pretty apparent.
fafalone Posted January 20, 2003 Posted January 20, 2003 On a more legitimate note, if we went around urinating and defecating everywhere, it would make us easier to track by predators.
Ahmad Posted January 21, 2003 Author Posted January 21, 2003 This is so funny. Funny, but not convinceable.
spuriousmonkey Posted March 17, 2003 Posted March 17, 2003 as for concise: most transgenic mice with a gene knocked out hardly have a phenotype. There is an awful lot of redundancy on the genetic and developmental level.
DocBill Posted March 18, 2003 Posted March 18, 2003 According to my friend Lynn Margulis, life has been at this now for almost 4 billion years 4^10. That's a lot of time to fix things. Bill
Deslaar Posted March 18, 2003 Posted March 18, 2003 Originally posted by DocBill According to my friend Lynn Margulis, life has been at this now for almost 4 billion years 4^10. That's a lot of time to fix things. Bill Yep....plenty of time. BTW you're a friend of Lynn Margulis??? :cool2: I have one of her books on my shelf, one of about 30 that I've yet to read.
Ahmad Posted March 19, 2003 Author Posted March 19, 2003 Still, that doesn't say why do we get to keep many things that make our lives more convenient, yet they are not necessary for our existance. While we don't keep many other things that we might as well have had.
DocBill Posted March 20, 2003 Posted March 20, 2003 Originally posted by Ahmad Still, that doesn't say why do we get to keep many things that make our lives more convenient, yet they are not necessary for our existance. While we don't keep many other things that we might as well have had. Life is supposed to be convenient? Damn. I got waaay gypted someplace. Call my lawyer.
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